shell的执行流控制

while true
read -p "please input filename: " FILENAME
do
  if [ "$FILENAME" = "exit" ]
  then
    echo exit
    exit
  elif [ ! -e "$FILENAME" ]
  then
    echo $FILENAME is not exist
  elif [ -f "$FILENAME" ]
  then
    echo $FILENAME is file
  elif [ -d "$FILENAME" ]
  then
    echo $FILENAME is directory
  fi
done

3.case语句

执行效率更高

case $1 in
	word1|WORD1)
	action1
	;;
	word2|WORD2)
	action2
	;;
	*)
	echo error
esac

4.expect

需安装expect

问题脚本

read -p "what's your name:" NAME
read -p "How old are you: " AGE
read -p "Which objective: " OBJ
read -p "Are you ok? " OK
echo $NAME is $AGE\'s old study $OBJ feel $OK

应答脚本

#!/usr/bin/expect
set timeout 1
set NAME [ lindex $argv 0 ]
set AGE [ lindex $argv 1 ]
set OBJ [ lindex $argv 2 ]
set FEEL [ lindex $argv 3 ]
spawn sh /mnt/ask.sh
expect {
"name" { send "$NAME\r";exp_continue }
"old" { send "$AGE\r";exp_continue }
"objective" { send "$OBJ\r";exp_continue }
"ok" { send "$FEEL\r" }
}
expect eof

将expect该为shell

#!/bin/bash
expect(){
/usr/bin/expect    <<EOF
spawn $5
expect {
"name" { send "$1\r";exp_continue }
"old" { send "$2\r";exp_continue }
"objective" { send "$3\r";exp_continue }
"ok" { send "$4\r" }
}
expect eof
EOF
}
expect su 12 shell ok "sh /mnt/ask.sh"

脚本练习

检测 172.25.254.1-172.25.254.10 网络是否开启

如果网络正常生成解析列表 hosts_list

格式如下

ip         主机名称

例如 ：172.25.254.1为开启状态主机名为westos_student1.westos.org

AUTO_SSH(){
/usr/bin/expect <<EOF
spawn ssh -l root 192.168.81.$1 $2
expect {
yes/no {send "yes\r";exp_continue}
password {send "shg12345\r"}
}
expect eof
EOF
}
 
if [ -e "/mnt/hosts" ]
then
  mv /mnt/hosts /mnt/hosts-`date +%T`
fi
 
for ID in 10 11 12
do
  ping -c1 -w1 192.168.81.$ID &> /dev/null && {
        echo -e "192.168.81.$ID\t`AUTO_SSH $ID hostname | tail -n 1 `" >> /mnt/hosts
}
done
 
for ID in 10 11 12
do
   ping -c1 -w1 192.168.81.$ID &> /dev/null && {
        AUTO_SSH $ID "scp /mnt/hosts root@192.168.81.$ID:/mnt"
}
done

读取一个用户列表文件，逐行创建用户，并在创建成功后输出提示信息。

if [ -z "$1" ]
then
  echo please input userlist following $0
elif [ ! -e "$1" ]
then
  echo $1 is not exist
else
  for name in `cat $1`
  do
     useradd $name && echo $name is createed
  done
fi

5.break,continue,exit,return

cobreak：用于提前退出循环。当在循环中遇到break语句时，循环会立即终止，程序会在循环之后继续执行。
 
continue：用于跳过当前循环的迭代并进入下一次迭代。当在循环中遇到continue语句时，代码将跳过对当前迭代的剩余语句，进入下一次迭代。
 
exit：用于提前终止程序。当遇到exit语句时，程序会立即停止执行并退出。
 
return：用于提前退出函数并将值返回给调用者。当在函数中遇到return语句时，函数将立即终止并返回指定的值给调用者。